scholarly journals Contrast detection thresholds of gabor strings: Configuration dependency

2005 ◽  
Vol 5 (8) ◽  
pp. 725-725
Author(s):  
D. Sagi ◽  
A. Judelman ◽  
Y. Bonneh
Keyword(s):  
Detection Thresholds ◽  
Contrast Detection

Frequency Dependence of Compliance Contrast Detection

2000 ◽  
Author(s):  
Neel Dhruv ◽  
Frank Tendick
Keyword(s):  
Virtual Environments ◽  
Haptic Perception ◽  
Low Frequency ◽  
Detection Sensitivity ◽  
Haptic Interface ◽  
Detection Thresholds ◽  
Contrast Detection ◽  
Spatial Frequencies ◽  
Contrast Thresholds ◽  
Varying Compliance

Abstract Psychophysical experiments were performed to investigate the haptic perception of objects with varying compliance over their surfaces. Perception of compliance contrast is important in interaction with soft environments, as in teleoperative surgery. Simulated surfaces were presented using a haptic interface in virtual environments. An adaptive 2–down, 1–up procedure was used to determine thresholds for compliance contrast detection at a range of spatial frequencies. The maximum effective temporal frequencies of compliance change, due to the subjects’ action of scanning the surfaces, were calculated. Force contrast detection thresholds were determined at a range of temporal frequencies to investigate the reliance of compliance contrast detection on force cues. Compliance and force discrimination thresholds were determined in order to compare with low frequency contrast thresholds. Compliance and force contrast detection thresholds were found to be 2% and 1% above 1/2 cyc/cm and 20 Hz, respectively. Both were significantly smaller than respective compliance and force discrimination thresholds and low frequency contrast detection thresholds. It appears that the improvement in compliance contrast detection sensitivity is due to subjects being more sensitive to force contrast at higher temporal frequencies. By changing environment exploration strategies or limb impedance, subjects may be able to change their sensitivity to object compliance contrast.

Perimetry of contrast detection thresholds of moving spatial sine wave patterns IV The influence of the mean retinal illuminance

1978 ◽  
Vol 68 (6) ◽  
pp. 860 ◽  
Author(s):  
Jan J. Koenderink ◽  
Maarten A. Bouman ◽  
Albert E. Bueno de Mesquita ◽  
Sybe Slappendel
Keyword(s):  
Sine Wave ◽  
Retinal Illuminance ◽  
Detection Thresholds ◽  
Contrast Detection ◽  
Wave Patterns ◽  
The Mean

Orientation-Tuned fMRI Adaptation in Human Visual Cortex

2005 ◽  
Vol 94 (6) ◽  
pp. 4188-4195 ◽  
Author(s):  
Fang Fang ◽  
Scott O. Murray ◽  
Daniel Kersten ◽  
Sheng He
Keyword(s):  
Visual Cortex ◽  
Separate Experiment ◽  
Detection Thresholds ◽  
Human Visual Cortex ◽  
Contrast Detection ◽  
Neurophysiological Studies ◽  
Short Term Adaptation ◽  
Almost All ◽  
Fmri Adaptation

Adaptation is a general property of almost all neural systems and has been a longstanding tool of psychophysics because of its power to isolate and temporarily reduce the contribution of specific neural populations. Recently, adaptation designs have been extensively applied in functional MRI (fMRI) studies to infer neural selectivity in specific cortical areas. However, there has been considerable variability in the duration of adaptation used in these experiments. In particular, although long-term adaptation has been solidly established in psychophysical and neurophysiological studies, it has been incorporated into few fMRI studies. Furthermore, there has been little validation of fMRI adaptation using stimulus dimensions with well-known adaptive properties (e.g., orientation) and in better understood regions of cortex (e.g., primary visual cortex, V1). We used an event-related fMRI experiment to study long-term orientation adaptation in the human visual cortex. After long-term adaptation to an oriented pattern, the fMRI response in V1, V2, V3/VP, V3A, and V4 to a test stimulus was proportional to the angular difference between the adapting and test stimuli. However, only V3A and V4 showed this response pattern with short-term adaptation. In a separate experiment, we measured behavioral contrast detection thresholds after adaptation and found that the fMRI signal in V1 closely matched the psychophysically derived contrast detection thresholds. Similar to the fMRI results, adaptation induced threshold changes strongly depended on the duration of adaptation. In addition to supporting the existence of adaptable orientation-tuned neurons in human visual cortex, our results show the importance of considering timing parameters in fMRI adaptation experiments.

Adaptation to peripheral flicker: Relationship to contrast detection thresholds

1990 ◽  
Vol 30 (3) ◽  
pp. 381-386 ◽  
Author(s):  
J.P. Harris ◽  
J.E. Calvert ◽  
R.S. Snelgar
Keyword(s):  
Detection Thresholds ◽  
Contrast Detection
Sign in / Sign up

Export Citation Format

Share Document